This invention relates generally to pipe severing apparatus and methods, and specifically to a method and apparatus for severing cast iron and other brittle pipe in a fast, safe manner, in a variety of sizes, and at various locations around a job site.
Previously, brittle pipe such as cast iron has been "cut" by a variety of methods. Most of these methods include the use of a chain having cutting wheels wrapped around the pipe and reciprocated by manual or mechanical means. However, it is well known that brittle materials, such as cast iron, vitreous clay, cement, and asbestos can actually be severed rather than cut, so that use of the reciprocating chain devices is no longer economical as it is a slower process.
Rather than using the reciprocating chain and cutting wheels procedure, it is known to hold the chain and cutting wheels in primarily fixed position while tensioning the chain. In this mode, the wheels are actually "stress inducing" wheels, and several wheels "dig" into the circumference of the brittle pipe, creating stress concentration points and initiating cracks that propagate from stress concentration to stress concentration, leading to catastrophic failure around the entire circumference.
Although advantageous, the unique property of these brittle materials to easily sever under stress can cause severe safety concerns where pipe severing is performed on a large scale, such as at residential and commercial construction sites, where cast iron, vitreous clay, cement, asbestos, and other brittle pipe materials are commonly used for plumbing and other end uses, due to their availability, ease of severing, and economic advantage. It would be advantageous if a pipe severing method and apparatus could be devised that would quickly and safely sever the pipe, preventing the two pieces from flying apart like projectiles. Further, many pipe severing devices currently used have configurations which allow the operator to easily have either one or both hands come close to the cutting chain. Some of these devices have foot pedals which actuate the chain, leaving the operator's hands substantially free, a potentially hazardous situation. Also, many of these devices are either fixed to the pipe to be severed, or are otherwise practically immobile so as to render them cumbersome at a residential or commercial construction site, where it would be convenient and advantageous to have a mobile device configuration. Still more advantageous would be a pipe severing device of the chain type which had simple means of keeping the chain substantially circular about the circumference of the pipe, so that many successive pieces of the same diameter could be quickly severed.